Approximately 75% of the adult population suffers from some form of periodontal disease. Periodontal disease results when virulent gram negative bacteria colonize the gingival crevice. This colonization involves specific interactions between bacterial adhesions and epithelial cell surface receptors. Secreted molecules found in serum, saliva, and crevicular fluid can also participate in these adhesion events. Porphyromonas gingivalis is a gram negative obligate anaerobe that is commonly isolated from periodontal pockets. Its adherence to oral epithelium is well documented, but the molecular basis for this interaction is unknown. Fibronectin is known to participate in a number of important adhesion events involving the integrin family of receptors, and a number of these receptors have been identified on epithelial cells. In addition, fibronectin can be expressed in an insoluble form on the surface of epithelial cells and also secreted by them. Also, soluble fibronectin is found in both saliva and serum. Finally, several bacterial strains have been identified which are able to bind various forms of human fibronectin. Thus the objective of this proposal is to determine the role of fibronectin in the adhesion of P. gingivalis to oral epithelial cells. Once the role of fibronectin in bacterial adhesion is determined, preventive therapies could to be developed which would inhibit this initial colonization event. Accordingly, the specific aims of this proposal are: (1) to characterize the interactions between P. gingivalis and fibronectin; (2) to characterize the fibronectin expression and/or fibronectin binding capacity of oral epithelium; and (3) to determine the potential role of fibronectin in the binding of P. gingivalis to oral epithelium. The ability of P. gingivalis to interact with either soluble and/or insoluble fibronectin will be determined by means of an ELISA. Both an epithelial cell line and freshly isolated oral epithelial cells will be analyzed by flow cytometry to determine the presence of cell surface fibronectin, receptors for fibronectin, and the ability of the receptors to bind fibronectin. Adhesion assays will be performed to determine the binding properties of P. gingivalis and oral epithelium. Importantly, the ability to use an established cell line as an in vitro model for bacterial adhesion in the oral cavity will also be investigated.